System Tray Icon Example bug if I change the current icon index to 0

[Kaguro]

Hi Guys!
I have a problem in the System Tray Icon Example in qt.
If I change this row:

iconComboBox->setCurrentIndex(1);

to:

iconComboBox->setCurrentIndex(0);

after this i have an error message in the debug:
"QSystemTrayIcon::setVisible: No Icon set"
And i dont see the icon in the tray menu, but if i set the default index to 1 as the original example, its working.
But Why? I dont understand what is the different between the 0. QComboBox icon and the 1. one?
Thanks your help!

[JonB]

@Kaguro
If you have code which you want run on QComboBox::currentIndexChanged but also for the initial situation, it is easiest to call it explicitly when you start.

Alternatively QComboBox::::currentIndex() starts at -1 on an empty combo box. If you have your signal connected before you populate it you should get the signal as it moves from -1 to 0 when you add the first item into the combo.

[Pl45m4]

@Kaguro said in System Tray Icon Example bug if I change the current icon index to 0:

I dont understand what is the different between the 0. QComboBox icon and the 1. one?

This line

    connect(iconComboBox, QOverload<int>::of(&QComboBox::currentIndexChanged), this, &Window::setIcon);

and the corresponding function

void Window::setIcon(int index)
{
    QIcon icon = iconComboBox->itemIcon(index);
    trayIcon->setIcon(icon);
    setWindowIcon(icon);

    trayIcon->setToolTip(iconComboBox->itemText(index));
}

The item at index 0 probably has no icon.

Edit:

Icon 0 should be the "bad" icon... Do you see that icon in your combobox and are you able to select it manually?

    iconComboBox = new QComboBox;
    iconComboBox->addItem(QIcon(":/images/bad.png"), tr("Bad"));
    iconComboBox->addItem(QIcon(":/images/heart.png"), tr("Heart"));
    iconComboBox->addItem(QIcon(":/images/trash.png"), tr("Trash"));

[Kaguro]

@Pl45m4 said in System Tray Icon Example bug if I change the current icon index to 0:

connect(iconComboBox, QOverload<int>::of(&QComboBox::currentIndexChanged), this, &Window::setIcon);

Yes I see the icon in my combobox and i can select it manually. One mention: Is there any chance the currentIndexChanged event is the issue? Because the default index is 0 in combobox, and if i want to use the 0. index the "currentIndexChanged" event is not execute because i didnt changed the index?

[JonB]

@Kaguro
If you have code which you want run on QComboBox::currentIndexChanged but also for the initial situation, it is easiest to call it explicitly when you start.

Alternatively QComboBox::::currentIndex() starts at -1 on an empty combo box. If you have your signal connected before you populate it you should get the signal as it moves from -1 to 0 when you add the first item into the combo.

[Kaguro]

@JonB Yeah thanks your help! This will be the solution! :)
Thanks Guys! @JonB @Pl45m4

[Pl45m4]

@Kaguro said in System Tray Icon Example bug if I change the current icon index to 0:

Is there any chance the currentIndexChanged event is the issue?

The signal even gets emitted when you change the idex programmatically.

• https://doc.qt.io/qt-5/qcombobox.html#currentIndexChanged

So something else must be wrong or you are doing something else wrong.

[JonB]

@Pl45m4
I'm only guessing for the OP, but looking https://doc.qt.io/qt-5/qtwidgets-desktop-systray-example.html#window-class-implementation the connect(iconComboBox, &QComboBox::currentIndexChanged) gets executed after iconComboBox gets populated? So if he wants it to be called initially he needs to do either of what I suggested?

[Pl45m4]

@JonB

I dont think it's necessary, because iconComboBox->setCurrentIndex(1 /* or 0 */); is called after the connection was set up and the combobox was filled.
Then it should emit currentIndexChanged anyways... but I could be wrong :)

(You would face the same situation when you add items to your comboBox in Design-Mode. The items are there, before you make any connections to your instances. setupUI would create the items and this is usually called first in any c'tor)

[JonB]

@Pl45m4
I have not tested this, and you may know more than I. But after the initial population the currentIndex will already be on 0, only then is the connect() executed. Then iconComboBox->setCurrentIndex(0) will not raise currentIndexChanged signal, and so not call the slot, but he wants it to be called, which I am assuming is the OP's situation?

Your design-mode description is indeed correct, and in this case again currentIndexChanged slots will not be called.

[Pl45m4]

@JonB said in System Tray Icon Example bug if I change the current icon index to 0:

Then iconComboBox->setCurrentIndex(0) will not raise currentIndexChanged signal, and so not call the slot, but he wants it to be called, which I am assuming is the OP's situation?

Yes, now I understand what you meant before :)